In common mobile communication networks two main techniques for a data transmission are used: circuit switched data transmission and packet switched data transmission. In the circuit switched domain a network establishes an interconnection for data transmission by allocating a radio channel to a mobile station, when a network host or service provider intends to transmit data via the network. Then data is transmitted via the network after the interconnection has been established. The radio channel is occupied by the mobile station during the entire duration of the interconnection, even though in many cases only a small amount of data has to be transmitted. However, regularly a subscriber is charged for the entire duration of the interconnection. This type of circuit switched data transmission is used in GSM (Global System for Mobile communications) networks.
In the packet switched domain the network transmits a data packet only when required, i.e. when data transmission has to be carried out. Thus, several mobile stations can use the same radio channel at a time. If a mobile station generates a data packet, the network routes that packet via a first unattached radio channel to a recipient. Thus, as data transmission frequently consists of data bursts, the radio channels can be used in an efficient manner. This type of packet switched data transmission is used in GPRS (General Packet Radio Service) systems.
However, the GPRS system may be provided as an additional service in existing GSM systems. Thus, a network develops that supports circuit switched as well as packet switched data transmission.
Recent packet data mobile stations enable access to the internet and to intranets. Therefore, the GPRS data transmission uses particularly the internet protocol (IP). If a mobile station is attached to a GPRS system and a PDP (Packet Data Protocol) context is activated, a terminal equipment is able to send data packets via the mobile station to the uplink. Vice versa, a host can use the downlink to send data packets to the terminal equipment. These data packets are routed by a gateway GPRS support node (GGSN) and a serving GPRS support node (SGSN) to the correct addresses.
However, before sending data packets the mobile station has to carry out a GPRS attach and a PDP context activation. The GPRS attach informs the network that the mobile station is available. The attach is established by the mobile station and the SGSN.
Furthermore, after the GPRS attach is established, the mobile station carries out a PDP context activation. The PDP context activation makes the mobile station known to the corresponding GGSN. Thereupon, data transmission via the GGSN to external networks is enabled.
Such PDP context activation may be requested by either the network or the mobile station. In GPRS systems and UMTS (Universal Mobile Telecommunications System), as described in technical specification “ETSI TS 123 060, V3.2.1 (2000-01)” published by the European Telecommunications Standards Institute, a network requested PDP context activation is used, when a GGSN receives a data packet to an address the corresponding mobile station has no PDP context active for. The GGSN sends a PDU (Protocol Data Unit) notification request to the mobile station, which decides based on the information contained in that request whether it wants to activate the PDP context in question or not.
However, in numerous cases a context activation is not desired from the mobile station point-of-view. In these cases the PDP context activation is refused or deactivated immediately by the mobile station. However, this is disadvantageously since a large amount of unnecessary PDP context activations is generated.